Questions for guys running 12-15 psi. - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 10-30-2008, 01:18 AM   #41
Elite Member
iTrader: (12)
 
Join Date: Jan 2007
Location: Hermosa Beach, CA
Posts: 2,575
Total Cats: 11
Default

Quote:
Originally Posted by Mangocats View Post
I have been running 12-16psi for a long time now, I have a simple mechanical wastegate control, and I think I last set the spring tension in 1999...

Believe it or not, you can control boost with the accelerator pedal. When I was having misfire problems at high boost, I just (tried) to keep my foot out of it to avoid experiencing the misfires.

As far as reliability, I'm around 90Kmi now and no engine problems so far. I drive as you describe, heavy foot, but shift before 6500 most of the time. Used to race a little, but I still shifted relatively early - my racing was harder on the brakes than anything else.

Most important thing for your engine safety is to get your fueling right. When in doubt, go for the rich side of ideal. Ignition timing retard hasn't done much for me in terms of eliminating knock problems, except in the 1000-2000 RPM range near WOT. Any other map area where I've had a knock, it has been a lack of fuel problem. I can still run a bit rich at 16psi / 7KRPM with 310 injectors, it seems that most kits are coming with larger ones these days, but in a stock 1.6 motor I haven't found a need for more than 310.

If I had socked away $100 a month toward a replacement motor, starting when I installed my turbo, I could afford a pretty sweet replacement engine by now:

Flyin' Miata : Engine/Drivetrain : Built engines : FM built stroker engine


WHAT?? No wonder you had a lack of fuel problem. Without running like a 12:1 FPR there is no way you are getting enough fuel out of 310 cc injectors for 16 psi of boost. And you will make less power with the car at 12 psi at full throttle compaired to 12 psi at 3/4 throttle.



Toddcod- Yep, all stock, all 100k miles of it.
cardriverx is offline   Reply With Quote
Old 10-30-2008, 09:56 AM   #42
!!! NOT CONFIRMED !!!
 
Join Date: Oct 2008
Posts: 15
Total Cats: 0
Default Loosely instrumented

It has been awhile since I did my tuning work, and I did the work off of datalogs from the LINK and a standard O2 sensor, so it's a rough guide at best, but... last time I checked, running near 15psi, I was reading rich across the band from 4000RPM up to 6500. I believe the injector duty cycle was near maxed out, but in reality, I try to keep things under 12psi most of the time anyway - over 12psi is just an artifact of cold weather for me.

I did keep my foot in it last night to test a new set of plugs and wires, and I did see 16psi - no knock or hesitation up past 6000RPM. Maybe when the kids are off to college, or at least old enough to enjoy hanging around a noisy garage all day (without getting into serious trouble), I can get the time to play on a dyno with a wideband O2 sensor, for now I just enjoy driving it.

Oh, and the way the LINK works, 12psi is 12psi, all fueling is governed by the MAP sensor which sees more or less exactly what my A-pillar gauge sees. The only affect that throttle position has is back pressure to the turbine compressor outlet. 12psi at WOT means that the wastegate is open enough to keep the turbine from making more than 12psi into the intake manifold. 12psi at 3/4 throttle indicates that there is more air pressure coming out of the compressor, and if you're not going to use that air, you could have gotten your 12psi with less exhaust back pressure because the wastegate could have been open a little wider.
Mangocats is offline   Reply With Quote
Old 10-30-2008, 10:21 AM   #43
!!! NOT CONFIRMED !!!
 
Join Date: Oct 2008
Posts: 15
Total Cats: 0
Default

Oh, and a tidbit from the past: stock 1.6 injectors are 220, and they were routinely used in turbo kits up to 7psi of boost or so (call it 7+15=22psi absolute), so, going from 220 to 310, you should be able to handle up to 31psi absolute, or about 16psi of boost.

Starting around 1998 or so, the "big boost" kit makers started running into people who were stroking their 1.8s and running 18+psi, so they quickly went up to 390s, then 440s as standard parts to avoid the label that their uprated injectors are too wimpy for real he-man power. I think they weren't really getting 390 flow out of their 390 injectors, probably due to the electrical portion of their systems, and it was a quicker / easier fix to go to a larger injector rather than fixing the the electrical drivers.
Mangocats is offline   Reply With Quote
Old 10-30-2008, 11:28 AM   #44
Elite Member
iTrader: (21)
 
paul's Avatar
 
Join Date: Jun 2006
Location: Point Pleasant, NJ
Posts: 2,957
Total Cats: 2
Default

Anyone else think this mangocats is talking out his ***?
paul is offline   Reply With Quote
Old 10-30-2008, 11:45 AM   #45
!!! NOT CONFIRMED !!!
 
Join Date: Oct 2008
Posts: 15
Total Cats: 0
Default

Quote:
Originally Posted by paul View Post
Anyone else think this mangocats is talking out his ***?
Ah, so the hazing begins....

Tanner and Cardell thought I was talking out my *** about the 310 injectors, but their standard program for the Link was lean as dry dog turds all over my map, when I scaled up master fuel for 310 injectors, it ran fine.

Believe me, or not, I really don't care.
Mangocats is offline   Reply With Quote
Old 10-30-2008, 12:02 PM   #46
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

Quote:
Originally Posted by paul View Post
Anyone else think this mangocats is talking out his ***?

not at all. i just found out 1.6L injectors are 220cc and are enough to support 7psi when you fix the "electrical drivers."


here's the math:

220cc = 20.95 lb/min

220cc = 43.5psi
7psi would put the rail at 57psi give or take
220cc injectors at 57psi = 252cc or 23.95 lb/min

23.95 x 85% duty cycle / .55 BSFC = 37.01 HP per cylinder

37 x 4 = 148BHP

the GT1241 can output around 15 lb/min
15 lb/min = 136BHP

so of course stock (220cc) injectors can handle a few pounds of boost through a GT1241.
Braineack is offline   Reply With Quote
Old 10-30-2008, 02:06 PM   #47
!!! NOT CONFIRMED !!!
 
Join Date: Oct 2008
Posts: 15
Total Cats: 0
Default

Braineack, your mama must be so proud...
Mangocats is offline   Reply With Quote
Old 10-30-2008, 02:30 PM   #48
Elite Member
iTrader: (12)
 
Join Date: Jan 2007
Location: Hermosa Beach, CA
Posts: 2,575
Total Cats: 11
Default

Quote:
Originally Posted by Mangocats View Post
Braineack, your mama must be so proud...
By running 16 psi on 330 cc injectors you either have the fuel pressure absurdly high, or are defying the laws of physics and flow calculations.
cardriverx is offline   Reply With Quote
Old 10-30-2008, 02:46 PM   #49
Elite Member
iTrader: (9)
 
TurboTim's Avatar
 
Join Date: Jun 2006
Location: Chesterfield, NJ
Posts: 6,485
Total Cats: 248
Default

Quote:
Originally Posted by Braineack View Post
not at all. i just found out 1.6L injectors are 220cc and are enough to support 7psi when you fix the "electrical drivers."


here's the math:

220cc = 20.95 lb/min

220cc = 43.5psi
7psi would put the rail at 57psi give or take
220cc injectors at 57psi = 252cc or 23.95 lb/min

23.95 x 85% duty cycle / .55 BSFC = 37.01 HP per cylinder

37 x 4 = 148BHP

the GT1241 can output around 15 lb/min
15 lb/min = 136BHP

so of course stock (220cc) injectors can handle a few pounds of boost through a GT1241.
I don't follow you because I am dumb.

7psi="a few" ?

220cc=43.5psi?

7psi would increase rail pressure to 57 if the nominal pressure is 50, right? (OEM reguators are 1:1?) but the pressure differential is still 50 across the injector, so assuming you have a 1:1 pressure regulator, your injector flow at xx duty cycle will be the same regardless of boost pressure.

My default link ECU settings for the RC440's/1.6 were pig rich.

I have only read this last page so I don't really know what this thread is about. But I did learn I could control boost with the accelerator pedal. ******* awesome. I can't wait to try.
TurboTim is offline   Reply With Quote
Old 10-30-2008, 03:06 PM   #50
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

ok let me revise my math...

220cc is rated at 43.5psi

220cc injectors rated at 50psi would now flow at 22.44 lb/min

22.44 * .85 / .55 = 34.68
34.68 * 4 = 138BHP

assuming 7psi on our little gt1241 would fully achieve it's potential on our 1.6L, then we have a good injector.


just laugh and stop picking my numbers apart, they were trivial, and i was trying to support his theory through the use of trickery.
Braineack is offline   Reply With Quote
Old 10-30-2008, 03:24 PM   #51
Elite Member
iTrader: (9)
 
TurboTim's Avatar
 
Join Date: Jun 2006
Location: Chesterfield, NJ
Posts: 6,485
Total Cats: 248
Default

Gotcha. I know what yous was up to. I'll agree with Paul.

RC440's at 80% duty cycle is 33.5lb/min
33.5/.55 (?) = 60.9
60.9*4=243hp

Ut oh. I guess I won't be making my 300rwhp at the dyno day. I am pretty sure my static fuel pressure is right at 43psi.

Where did you get the .55 BSFC #?

oh, "haha"
TurboTim is offline   Reply With Quote
Old 10-30-2008, 03:26 PM   #52
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,900
Total Cats: 1,792
Default

just run them to 100%, wont hurt nothing.


In all honesty, i dunno were BSFC should be.. i always use .55 for my math. My 460cc injectors are seeing 85% at 232rwhp and 12:1.
Braineack is offline   Reply With Quote
Old 10-30-2008, 03:32 PM   #53
Elite Member
iTrader: (9)
 
TurboTim's Avatar
 
Join Date: Jun 2006
Location: Chesterfield, NJ
Posts: 6,485
Total Cats: 248
Default

Quote:
Originally Posted by Braineack View Post
just run them to 100%, wont hurt nothing.


In all honesty, i dunno were BSFC should be.. i always use .55 for my math. My 460cc injectors are seeing 85% at 232rwhp and 12:1.
yeah I'm not too worried about them. I wonder what I'm doing "wrong" though to get enough fuel out of them. Must be the fuel rail

Quote:
Originally Posted by Mangocats View Post

If I had socked away $100 a month toward a replacement motor, starting when I installed my turbo, I could afford a pretty sweet replacement engine by now.
If I had socked away $1 for each Braineak post, I could afford a pretty sweet replacement engine by now. hehe
TurboTim is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM
wiring wideband ground to battery terminal btabor ECUs and Tuning 10 09-28-2015 06:33 PM
WTB: Megan EZ street coilovers Rhidell WTB 1 09-26-2015 05:27 PM
E-Manage Base Maps faviles5566 ECUs and Tuning 0 09-04-2015 12:50 PM
E-Manage Base Maps faviles5566 ECUs and Tuning 0 09-04-2015 12:50 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 07:48 PM.